In this proposal, the intent is to determine the safety, therapeutic effect and immunological effects of interferon gamma given subcutaneously to patients with refractory non-tuberculous mycobacterial infections. The treatment protocol consists of a one year or longer treatment course of a standard dose of interferon gamma. It is anticipated, and in fact hoped, that interferon gamma therapy will result in enhancement of the antimycobacterial immune responses in these patients. The main questions that must be answered in this phase I/II trial are whether the immune response will be tolerable and whether interferon gamma will elicit a sustained clinical response in patients with refractory non-tuberculous mycobacterial infections. Thus far, the interferon gamma injections have been tolerated by most patients with few side effects; mainly fevers, chills, and myalgia. Of the 19 patients who have been enrolled in the protocol, 7 pts have improved during the course of study, 2 pts have remained stable, 4 pts have worsened and have thus been dropped from the study, 1 opted out of the study after 5 months and the follow-up data is pending, and 5 have not been on the protocol long enough to evaluate their status.